Sealing arrangement comprising lips for prosthetic shafts

ABSTRACT

A prosthetic socket seal includes at least one radially projecting sealing lip which jointly with a base subtends an annular gap. This annular gap is vented on a proximal side by the external atmosphere, resulting in creation of a pressure gradient at the sealing lip that produces stronger compression of the sealing lip against the prosthetic socket with increasing partial vacuum on a distal side of the sealing lip.

[0001] Residual limbs of amputees are inserted like a piston in acup-shaped prosthetic socket. Also, it is known to utilize atmosphericair pressure to retain the prosthetic socket on the residual limb. Theresidual limb for this purpose must be kept hermetically sealed againstthe inner prosthetic socket wall or against a liner pulled over theresidual limb.

[0002] With proper sealing, a force applied to remove the prostheticsocket from the residual limb will generate a partial vacuum that reactsagainst the force. On the other hand the retention force collapsesimmediately when air enters a gap between said residual limb and theprosthetic socket.

[0003] The European patent application EP 0 632 765 discloses aprosthetic socket fitted with a seal which maintains sealing between theresidual limb and the prosthetic socket.

[0004] For that purpose the prosthetic socket is fitted with aperipheral groove located a distance from its distal end and whichreceives a sealing ring. The sealing ring consists of an annular corecovered with a layer of elastomer. A sealing lip is formed on said ringand extends toward the inside area of the prosthetic socket.

[0005] The purpose of the sealing lip—which hugs the skin of theresidual limb is to compensate for the diameter fluctuations of theresidual limb. Because the prosthetic socket is made of a rigidmaterial, its inside diameter is constant. On the other hand, theresidual limb volume changes over the long-term and the short-term. Thelong-term fluctuations are caused by changes in tissue volume, whereasthe short-term fluctuations depend on the residual limb's blood pressureand circulation within the residual limb. It is known that at highertemperatures the extremities tend to swell while at low temperaturestheir diameters shrink. This phenomenon may be observed for instanceeven in a healthy individual at his watch band.

[0006] The lip seal is folded toward the closed prosthetic socket endwhen the patient inserts a residual limb into the prosthetic socket. Thelip seal will then rest against the residual limb solely on account ofbeing prestressed.

[0007] The moment a force is applied to remove the prosthetic socketfrom the residual limb, a slight partial vacuum is set up between theresidual limb and the prosthetic socket space between the distal end andthe lip seal. The magnitude of the said partial pressure isapproximately proportional to the extent of the annular gap between theresidual limb and the prosthetic socket.

[0008] With respect to the prior art, the pressure difference at the lipseal is in a direction lifting said lip seal from the residual limb,thereby allowing air to enter the annular gap and, on account of theensuing loss of partial vacuum, retention is lost.

[0009] The magnitude of the admissible partial vacuum at which thesealing lip would detach depends on the radial prestressing force bywhich the sealing lip rests against the residual limb. It is observedthat a comparatively large prestressing force is required, which in turnmay entail interference in the blood circulation in the region betweenthe sealing lip and the distal end of the residual limb.

[0010] Accordingly, the objective of the present invention is to createa seal the sealing effect of which is substantially independent of aprestressing force magnitude.

[0011] This problem is solved in the present invention by the sealhaving the features of claim 1.

[0012] In this new seal, the base is seated on the residual limb.

[0013] The sealing lip originates at the base and at its edge pointsproximally. When the residual limb jointly with said seal has beeninserted into a cup-shaped prosthetic socket—which moreover is air tightin the region between the sealing lip and the distal end—a partialvacuum will arise as soon as a force tending to remove the prostheticsocket from the residual limb has been applied. If the sealing lipshould enclose the residual limb discontinuously, then the end of thissealing lip should be bonded to the base.

[0014] Means associated with the sealing arrangement ventilates the rearof the sealing lip, so that atmospheric pressure prevails at the sealinglip between it and the residual limb. The opposite side of the sealinglip resting against the inside wall surface of the prosthetic socket isexposed to the more or less pronounced partial vacuum in said socket.

[0015] Accordingly, a pressure gradient exists at the sealing lip andthe direction of the gradient is such that it will increasingly pressthe sealing lip against the prosthetic socket as the partial vacuumincreases and thereby will improve air tightness.

[0016] As regards the new seal, the sealing effect is independent of themagnitude of the initial force pressing the sealing lip against theprosthetic socket. Self-reinforcing compression is at work the momentthe partial vacuum in the prosthetic socket increases. Air leakstherefore cannot occur on the base side.

[0017] The base may be made sufficiently large in the residual limblongitudinal direction such that excellent air tightness shall beattained even with low compression forces.

[0018] The compression applied to the residual limb may be decreased byfitting the seal at the base with at least one other sealing lip runningin the same direction as the seal which seals off the prosthetic socket,the former sealing lip being primarily configured to seal off the saidresidual limb. Again, the gap between the two sealing lips isback-vented in order to provide atmospheric pressure between them.

[0019] A cuff-shaped base running above the root of the sealing lipwhich seals against the prosthetic socket operates as a second sealinglip and extends proximally over the root of said sealing lip. Thesupport itself acts as a second sealing lip which is flexible enough tofollow the local contours. As a result a small prestressing force may beused without degrading the air tightness relative to the residual limband the prosthetic socket.

[0020] In order not to degrade the air tightness, the particular sealinglips are adequately stretchable in the residual limb peripheraldirection.

[0021] Another way to retain the sealing lip against the prostheticsocket even when a definite gap arises on account of residual limbvolume changes between the residual limb and the prosthetic socket, isto use magnetic particles in the sealing lip and ferromagnetic particlesin the prosthetic socket. In the manner of a magnetic locking means, thesealing lip automatic will be drawn to the prosthetic socket.

[0022] The magnetized particles may be present selectively in theprosthetic socket or in the sealing lip while the other component maycontain unmagnetized, ferromagnetic particles.

[0023] The sealing lip base selectively may be a separate cuff directlyworn on the skin or on an external, appropriate liner, or the cuff maybe formed of the liner itself.

[0024] The back-venting means may be a simple annular groove runningalong the sealing lip and configured in such a way that even in the mostadverse case its opening will be maintained and the sealing lip will bevented by the external atmosphere by means of a pressure compensatingduct in the cuff or in the liner.

[0025] The back-venting means simultaneously may also be used to keepthe sealing lip spaced from the base or liner, for instance when theseal is used for a residual limb containing low-resiliency tissue, forinstance in the case of below-knee prostheses. The back venting spacerassures that even in the event of volume loss, the sealing lip shallrest on account of its basic prestressing force against the inside wallsurface of the prosthetic socket. In this manner prosthetic sockets maybe used that may be fitted immediately following surgery, that is beforethe residual limb has shrunk. The loss of volume normally would entailleakage, which however the new seal easily precludes.

[0026] For such a purpose, the spacers shall be advantageouslycompressible and air-permeable in order not to interfere with backventing. Open-cell foam is an appropriate material for this purpose.

[0027] Another way to attain the required prestressing force is toimpart a basic prestressing force to the sealing lip pointing toward thesocket in such manner that the sealing edge automatically adjusts itselfto a cross-section exceeding that defining the root.

[0028] Another objective of the present invention is to create aprosthetic socket both able to cooperate with the seal and containingferromagnetic particles in its sealing lip facing the prosthetic socket.

[0029] In this design the socket also contains ferromagnetic particleswhich may be selectively magnetized or not in order to tightly attractthe sealing lip against the inside wall surface of the prostheticsocket.

[0030] Other features of the present invention are recited in thedependent claims. Moreover combinations of features for which noexplicit illustrative embodiment is offered herein also shall beconstrued as being claimed.

[0031] The appended drawing show illustrative embodiments of the presentinvention.

[0032]FIG. 1 is a longitudinal section of a first illustrativeembodiment of a seal according to the invention,

[0033]FIG. 2 shows the configuration of the seal of the invention in aprosthetic socket,

[0034]FIG. 3 is a longitudinal section of a liner fitted with the sealof the invention, and

[0035]FIGS. 4, 5 are each a longitudinal section of a further embodimentof the seal of the invention.

[0036] In a schematic manner, FIG. 1 shows a seal 1 designed to seal offa residual limb relative to the inside volume of a prosthetic socket forthe purpose of keeping the said socket against the residual limb bymeans of a partial vacuum, i.e. to enhance its affixation to theresidual limb.

[0037] The seal 1 comprises a cuff-like base 2 having a proximal endface 3, a distal end face 4, and an inside surface 5 and an outsidesurface 6.

[0038] The cuff-like base is tubular in the broadest sense and is formedof an air tight, elastically stretchable material. The diameter of saidbase 2 is selected in a manner that it may be properly seated on aresidual limb while being very minimally prestressed. A peripheralsealing lip 7 is affixed on the outside surface 6 of the base 2 andcomprises a root 8 and a sealing edge 9 extending away from said root.The sealing lip 7 also is shaped like an annulus peripherallysurrounding the outside surface 6 of the base 2.

[0039] The root 8 is hermetically bonded to the outside surface 6.

[0040] The bonding area also constitutes a peripheral and closed ringand only runs in the longitudinal direction of the base 2 over a smallfraction of the height of the sealing lip 7 in the embodiment of FIG. 1.As a result, a cross-sectionally conical annular gap may extend abovethe bonding site of the root 8 between the outside surface 6 and thesealing lip 7. An annular filler element or spacer 11 made of anopen-cell foam material is located between the side of the sealing lip 7facing the outside surface 6 and this latter surface in order toconstrain the said annular gap. The ring has a cross-sectionally conicalstructure and is inserted in a way that its narrow end points toward theroot 8.

[0041] The sealing edge 9 is kept a distance from the outside of the ofthe base 6 by the annular spacer 11. The annular gap extends between theoutside surface 6 and the radially inward side of the sealing lip 7 soas to be permanently vented by the external atmosphere.

[0042] By means of this annular and conical spacer 11, said gap also ispreserved when the base 2 is peripherally enlarged. The radial wideningof the base 2 is transmitted by the spacer 11 to the sealing lip 7 andhence also to the sealing edge 9.

[0043]FIG. 2 shows the new seal 1 in use.

[0044]FIG. 2 in a simplified manner shows an above-the-knee prosthesis15 which comprises a cup-shaped prosthetic socket 16, an adapter 17, anartificial knee-joint 18, an artificial lower leg 19 and an artificialfoot 21.

[0045] The prosthetic socket 16 is hermetically sealed at its distal endand is fitted with an inside wall surface 22 which is smooth at least insome areas.

[0046] During use, the seal 1 shown in FIG. 1 is slipped over theabove-the-knee residual limb in a manner such that the sealing lip 9extends proximally and the base 8 is located distally on the residuallimb 23. Next the patient by his/her above-the-knee residual limb 23enters the cup-shaped prosthetic socket 16 until the residual limb canproceed no deeper. A valve (omitted) assures that the air in front ofthe residual limb 23 may escape from the prosthetic socket 16.

[0047] In the operational position, the sealing edge 9—or an axial areabeginning at the sealing edge 9 and running some distance in thedirection of the root 8—will rest against the inside wall surface 22 ofthe prosthetic socket 16. This prosthetic socket 16 is smooth, at leastin this strip-shaped region where it cooperates with the sealing lip 7,in order to attain the desired sealing effect.

[0048] The annular spacer 11 assures that the sealing edge 9 constantlyrests against the inside wall surface 22. Moreover, on account of itsopen cell nature, the spacer provides assurance that the gap between thesealing lip 7 and the base 2 will be ventilated by the externalatmosphere.

[0049] In the drawing it is assumed that the prosthetic socket 16 issufficiently wide above the seal 1 that, above this seal 1, thepatient's tissue will not rest everywhere against the inside socket wall22 and will not hamper ventilating of the gap between the sealing lip 7and the base 6.

[0050] If such risk were expected, then a borehole 24 may be providedjust above the expected position of the sealing edge 9 to act as apressure balancing duct and optionally to communicate with severalgrooves the widths of which would be selected to be small enough so theycould not be filled by the tissue of the residual limb 23. The positiveventilation of the open-cell spacer 11 would take place through suchgrooves.

[0051] When the prosthetic socket is exposed to a force tending to pullthe prosthetic socket 16 off the residual limb 23, there will occur amore or less marked partial vacuum in the distal space between thesealing lip 9 and the base of the prosthetic socket 16. Said partialvacuum acts on the outside of the sealing lip 7, while the inside orback side of the sealing lip 7, namely the side facing the base 2, isoccupied by atmospheric pressure. As a result there is a pressuregradient at the sealing lip 7 whereby, as the partial vacuum increases,the compression of the sealing lip 7 against the wall inside surface 22of the prosthetic socket 16 also increases. The compression isapproximately proportional to the pressure difference across the sealinglip.

[0052] Thus, according to the state of the art, the pressure gradientacross the sealing lip extends in the opposite direction and tends todetach the sealing lip as it increases, that is as the pressuredecreases; with the present invention, on the other hand, the sealinglip is increasingly compressed more and more against the inside wallsurface 22 of the prosthetic socket 16.

[0053] The prestressing force at rest by which the sealing edge 9 isforced against the inside wall surface 22 is practically without effecton the air tightness in the presence of high partial vacuum, that iswith a high removal force.

[0054] In order to remove the above-knee prosthesis 15, the patientconventionally activates a valve on the prosthetic socket 16 in order toaerate the space below the seal 2 to enable extracting the residual limb23 out of the prosthetic socket 16.

[0055] The seal 2 of the invention is described above with respect to anabove-knee prosthesis. It is clear however that the seal 2 also may beused with prostheses used for residual limbs containing little softtissue, for instance below-knee prostheses. The spacer 11, which alsoassures back venting of the sealing lip 7, simultaneously also operatesas a balancing component between the residual limb cross-section at thelevel of the seal 2 and the inside cross-section of the respectiveprosthetic socket at that location.

[0056] Even those suction sockets which are comparatively large relativeto the residual limb can still be affixed firmly and reliably when usingthe new seal 2. Such condition arises when a prosthesis is fitteddirectly following amputation. The residual limb atrophies with time,becoming too large and losing an air tight condition. By using the newseal 1, the prosthesis again may be reliably affixed.

[0057] The embodiment shown in FIG. 2 assumes that the seal 1 is seateddirectly on bare skin.

[0058] To attain adequate air tightness, a less flexibly adapting baserequires either a comparatively large prestressing force, or this base 2must be made elongated. The radial prestressing force may be reduced ina base 2 which is long as seen in the residual limb's longitudinaldirection.

[0059] Instead of pulling the seal 1 directly on the bare skin, it mayalso and obviously be set on the top side of an appropriate liner whichshall be air tight in the region of the seal 1.

[0060]FIG. 3 shows an embodiment of the seal 1 of the invention. In thisdesign the base constitutes a liner 25 in the form of a conventionalsleeve. The sealing lip 7 is adhesively bonded to the outside of theliner 25 at a distance from its distal end. The connection between theliner 25 and the sealing lip 7 assumes the same form as alreadycomprehensively discussed above in relation to FIG. 1. A repeat of thisdescription is therefore unnecessary.

[0061] The sealing lip 7 of the embodiment shown in FIG. 1 runs axiallyin such manner that it entirely disappears within the prosthetic socket16 when the prosthesis 15 is worn.

[0062]FIG. 3 shows in dashed lines a sealing lip 7′ which normallyprojects beyond the proximal end of the liner or of the prostheticsocket 2. When in use, it will be folded outwardly over the proximal rimof the prosthetic socket 2 as indicated in FIG. 3 by 7″. In some casesthe spacer 11 may be eliminated from such a configuration because thewidth of the insertion aperture of the prosthetic socket perforceradially pulls the sealing lip 7 from the liner 25 and thus provides therequired back venting.

[0063] The means back venting the sealing lip 7 virtually consists inthe proximal extension of the sealing lip 7, allowing folding over ofthe proximal rim of the prosthetic socket.

[0064]FIG. 4 illustrates a very simple design of a cuff-like seal. Theseal 1 in this case consists of a plain soft tubular segment which isfolded on itself at a fold line 26. The fold line 26 simultaneously actsas the root of the external sealing lip 7 and allows subtending an innersealing lip 27 having the same material properties as the sealing lip 7.The spacer 11 is inserted in the manner already described above betweenthe two sealing lips 7 and 27.

[0065] In this respect the fold 26 may be considered as both the root ofthe sealing lip 7 and the root of the sealing lip 27, that is the sameas the base 2. The air tightness provided by the sealing lip 27 relativeto the residual limb is the same as described above in relation to thesealing lip 7.

[0066] The embodiment of FIG. 4 offers the advantage of especiallysimple construction.

[0067] To preclude the sealing lips 7 and 27 from shifting axiallyrelative to one another, they may be locally bonded adhesively near thefold 26.

[0068] Lastly FIG. 5 shows a seal 1 consisting of a soft tubular base 2the wall of which is slightly slit open axially. The result is anexternal sealing strip 28. A second soft tubular element 29 isadhesively bonded or vulcanized on the outside of the tubular support,after having been axially stretched before said bonding orvulcanization. As soon as the connection zone has cured, the externallyapplied force is removed and the outer element 29 is cut to the lengthof the inner support 2. The outer tube 27, being axially prestressed,will tend to bend the strip 28 radially outward. The inner portion ofthe slit region acts like the inner sealing lip 27 of the embodimentmode of FIG. 4.

[0069] A prosthetic socket seal comprises at least one radially externalsealing lip which jointly with a base subtends an annular gap. Saidannular gap is vented by the external atmosphere and as a result apressure gradient is created at the sealing lip, whereupon said gradientwill impose a larger compression of said sealing lip against theprosthetic socket when the partial vacuum becomes larger.

1-17. (Canceled).
 18. A seal for sealing a residual limb within acup-shaped air tight prosthetic socket comprising: a base adapted to bepulled onto a residual limb and to enclose at least a portion of aresidual limb peripherally, at least one sealing lip having a root and aflexibly compliant sealing edge that is spaced from the root and isarranged so as to hermetically rest against an inner wall area of aprosthetic socket and which is affixed by its root to the base; saidsealing lip open to ambient air between its connection with the base andits sealing edge; said lip extending along a longitudinal direction ofthe base and diagonally diverging therefrom at least in part.
 19. Sealas claimed in claim 18, wherein the base and sealing lip are annular.20. Seal as claimed in claim 18, wherein the base comprises at least asecond sealing lip which comprises a second sealing edge that is spacedfrom the root and is configured to hermetically rest against a residuallimb, and wherein the second lip extends peripherally and continuouslyto enable the second sealing lip to enclose a residual limb, and furtherwherein the second sealing lip is affixed by its root to said base. 21.Seal as claimed in claim 18, wherein said sealing lip is elasticallystretchable at least in a direction parallel to the sealing edge. 22.Seal as claimed in claim 21, wherein when the seal is in an operationalposition on a residual limb, the sealing edge of the sealing lip extendstoward a proximal end of a residual limb.
 23. Seal as claimed in claim18, wherein the sealing lip is made of a material that may elasticallyclosely conform to a contour.
 24. Seal as claimed in claim 18, whereinsealing lip contains magnetized ferromagnetic particles.
 25. Seal asclaimed in claim 18, wherein the base comprises a prosthetic suctionliner which is air tight at least in the vicinity of the root of thesealing lip.
 26. Seal as claimed in claim 18, wherein the base comprisesa cuff which is adapted to engage a residual limb in an air tight mannerat least in the region of the root.
 27. Seal as claimed in claim 18,including a venting device comprising a spacer located between the baseand the sealing lip, said spacing maintaining the area between the baseand the sealing lip open to ambient air.
 28. Seal as claimed in claim10, wherein the spacer is resiliently compressible.
 29. Seal as claimedin claim 18, wherein the sealing lip is configured in a manner to form abend pointing away from the residual limb whereby, in its operationalposition, the sealing edge of the sealing lip subtends a cross-sectionalsurface which is larger than that subtended by the root of the sealinglip.
 30. Seal as claimed in claim 27, wherein the spacer is made ofopen-cell foam.
 31. Seal as claimed in claim 27, wherein the spacer runsperipherally along the sealing lip at least over nearly a full length ofthe seal.
 32. Seal as claimed in claim 18, wherein the sealing lip has alength measured between the root and the sealing edge such that said lipmay be outwardly folded over itself.
 33. Prosthetic socket using a sealas defined in claim
 18. 34. Prosthetic socket as claimed in claim 34,wherein the seal contains magnetized or unmagnetized ferromagneticparticles in its socket wall at least in the region which is oppositethe sealing lip of the seal.